1. Field of Invention
The invention relates to the field of power electronics.
It is based on a converter arrangement according to the preamble of the first claim.
2. Discussion of Background
Such a converter arrangement has already been described, for example, in the German Laid Open Specification DE 40 23 687 A1.
This is a so-called U-converter, that is to say a converter having a DC intermediate circuit and a capacitor bank. Such a converter normally comprises a plurality of phases, which each comprise two branch modules. The branch modules have at least two switch modules which are connected in series and, with their center connection, form a load connection. Either the positive voltage or the negative voltage of the DC intermediate circuit is connected to the load connection by switching the switches in one branch on and off alternately.
In contrast to this, so-called I-converters were primarily used until a short time ago, that is to say converters which have a large inductance instead of a capacitor bank, which large inductance decouples the two three-phase bridges. Since there was thus already a large inductance in the intermediate circuit anyway, the circuit arrangements did not need to be optimized with respect to parasitic inductances.
However, the influence of parasitic inductances in the case of U-converters is now not negligible. Particularly during commutation of the current from one bridge branch to the other, the commutation current should be opposed by as little inductance as possible in order that as little voltage as possible occurs across the semiconductor, in accordance with UL=L*(di/dt), during the changeover.